Which fictional doctor is House M.D.’s chief oncologist and best friend?

James Wilson is House M.D.’s chief oncologist and best friend. Robert Sean Leonard portrays Wilson throughout the series.

Wilson works at Princeton-Plainsboro and provides a compassionate counterpoint to House’s confrontational personality. As an oncologist, he treats patients with cancer, while as House’s friend he often explains social consequences that House dismisses or overlooks.

Their friendship is central to the series. Wilson frequently helps House through professional and personal crises, although House’s manipulation and disregard for boundaries repeatedly strain the relationship. Their contrasting personalities—House’s skepticism and Wilson’s empathy—drive many of the show’s character stories.

The question refers to Wilson’s fictional role, not the actor’s real profession. Robert Sean Leonard is an American actor, while James Wilson is the oncologist. Wilson also has complicated family and romantic storylines, but his defining connection in the series is his long friendship with Gregory House.